• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.27-33
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• 2012

A marine propeller is designed for preventing cavitation priority. Cavitation is a phenomenon which is defined as the vibration or noise by dropping the pressure on the high-speed rotation of the propeller. There has to be a enough thrust on the low-speed rotation for preventing cavitation. Thus, it has to be considered in the increasing of the number of blade and the angle of wing to design the propeller. In addition, flow resistance will be increasing by narrowing the width between blades. So high quality surface roughness of the hub to minimize flow resistance is required. Interference problems with tool and neighboring surfaces often take place from this kind of characteristics of the propeller. During 5-Axis machining of these propellers, the excessive local interference avoidance, necessary to avoid interference, leads to inconsistency of cutter posture, low quality of machined surface. Therefore, in order to increase the surface quality, it is necessary to minimize the cutter posture changes and create a continuous tool path while avoiding interference. This study, by using a MC-space algorithm for interference avoidance and a MB-spline algorithm for continuous control, is intended to create a 5-Axis machining tool path with excellent surface quality. Also, an effectiveness is confirmed through a verification manufacturing.

• Journal of Drive and Control
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• v.5 no.1
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• pp.3-10
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• 2008

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.579-592
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• 2016

CNUSAIL-1, to be launched into low-earth orbit, is a cubesat-class satellite equipped with a $2m{\times}2m$ solar sail. One of CNUSAIL's missions is to deploy its solar sail system, thereby deorbiting the satellite, at the end of the satellite's life. This paper presents the design results of the attitude control system for CNUSAIL-1, which maintains the normal vector of the sail by a 3-axis active attitude stabilization approach. The normal vector can be aligned in two orientations: i) along the anti-nadir direction, which minimizes the aerodynamic drag during the nadir-pointing mode, or ii) along the satellite velocity vector, which maximizes the drag during the deorbiting mode. The attitude control system also includes a B-dot controller for detumbling and an eigen-axis maneuver algorithm. The actuators for the attitude control are magnetic torquers and reaction wheels. The feasibility and performance of the design are verified in high-fidelity nonlinear simulations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.71-72
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• 2013

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.289-290
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• 2006

In general, atomic force microscope (AFM) used for metrological purpose has measuring range less than a few hundred micrometers. We design and fabricate an AFM with long measuring range of $200mm{\times}200mm$ in X and Y axes. The whole stage system is composed of surface plate, global stage, microstage. By combining global stage and microstage, the fine and long movement can be provided. We measure the position of the stage and angular motions of the stage by laser interferometer. A piezoresistive type cantilever is used for compact and long term stability and a flexure structure with PZT and capacitive sensor is used for Z axis feedback control. Since the system is composed of various actuators and sensors, a real time control program is required for the implementation of AFM. Therefore, in this work, we designed a multi-axis control program using a FPGA module, which has various functions such as interferometer signal converting, PID control and data acquisition with triggering. The control program achieves a loop rate more than 500 kHz and will be applied for the measurement of grating pitch and step height.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1439-1443
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• 2007

In this paper, vibration reduction techniques of a voice coil motor (VCM) actuator are presented for AFM imaging system. The damping coefficient of the actuator driven by VCM with a flexure hinge is quite low and it cause the about 30dB peak amplitude response at the resonance frequency. To decrease this peak response, we design and apply elliptical band-stop filters to xy and z axis VCM actuator. Frequency response of each actuator with filter is measured to verify the effect of the filters. As a sensor, capacitive sensor is used. Vibration reduction rate of the xy actuator with the filter is also measured while real AFM scanning condition. As another method, closed loop control with the capacitive sensor is applied to the xy axis actuator to add an electrical damping effect and vibration reduction rate measured. These vibration reduction rates with each method are compared. In the case of z axis actuator, the frequency response of force (gap) control loop is measured. For comparison, the frequency response using a conventional PID controller is also obtained. Finally, the AFM image of a standard grid sample is measured with the designed controller to analyze the effect in the AFM imaging.

• Journal of Industrial Technology
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• v.40 no.1
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• pp.19-23
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• 2020

In this paper, we proposed a PC-based CNC control system using EtherCAT-based servo drive and I/O device. The default communication of LinuxCNC is a parallel port, and data processing with high bandwidth is impossible. However, it is possible to apply various bandwidth devices through the application of EtherCAT, one of the industrial Ethernet communications with high bandwidth. Therefore, the hardware control method of LinuxCNC was applied through EtherCAT communication from the existing parallel port. Finally, through HAL configuration, I/O device operation check and 3-axis motion control proved the LinuxCNC system with EtherCAT.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.441-443
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• 2007

In this paper, The authors design the current controller which independently control the d, q axis current transformed by the synchronously rotating d, q axis and a Space Vector Pulse Width Modulation(SVPWM) to steadily control the output DC-Link voltage against the variable load of the three phase PWM converter. Also, This study improves the high power factor, stability, and rapid response by the phase angle control using the digital Phase Locked Loop(PLL).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.3
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• pp.505-514
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• 1994

Koreasat spacecraft requires accurate and reliable attitude control to provide beam pointing for tenyear long communication and direction broadcasting services. This paper describes the detailed design and performance of an on-orbit normal mode attitude control subsystem for the spacecraft. Koreasat used a momentum wheel which has nominal momentum 475in-1b sec(547.6cm-kg sec) aligned with the pitch axis to control pitch attitude and provide gyroscopic stiffness in roll/yaw plane and used a 300 atm magnetic torquer to control the roll and yaw attitudes. An Earth Sensor Assembly (ESA) is used to provide pitch and roll information for the on-board micropocessor. The roll/yaw control used bang-off-bang control and while pitch axis control used proportional and integral control law. Control system errors during the operational normal mode are 0.03 deg, 0.1 deg and 0.01 deg in roll, yaw and pitch axes, respectively. Current attitude control system provides adequate control performances to capture initial attitude errors and spacecraft nutation.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.11
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• pp.664-670
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• 2004

This paper presents a new velocity estimation strategy of a non-salient permanent magnet synchronous motor (PMSM) drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system that has the information of rotor position error. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error to zero. For zero and low speed operation, PI controller gains of rotor position tracking controller have a variable structure according to the estimated rotor velocity. In order to boost the bandwidth of PI controller around zero speed, a loop recovery technique is applied to the control system. The proposed method only requires the flux linkage of permanent magnet and is insensitive to the parameter estimation error and variation. The designers can easily determine the possible operating range with a desired bandwidth and perform the vector control even at low speeds. The experimental results show the satisfactory operation of the proposed sensorless algorithm under rated load conditions.